青海省纳日贡玛斑岩钼铜矿床成矿花岗斑岩锆石LA-ICP-MSU-Pb定年及地质意义  

Zircon LA-ICP-MS U-Pb Dating for Narigongma Porphyry Molybdenite-copper Deposit in Southern Qinghai Province and Its Geological Implication

作　　者：郝金华[1,2] 陈建平[2] 董庆吉[2] 田永革[3] 李玉龙[3] 陈冬[4] 

机构地区：[1]中国地质大学科学研究院,北京100083 [2]中国地质大学北京市国土资源信息开发研究重点实验室,北京100083 [3]青海省地质调查院,青海西宁810012 [4]中国黄金集团公司,北京100011

出　　处：《现代地质》2012年第1期45-53,共9页Geoscience

基　　金：中国地质调查局地质调查项目(1212010630804;1212011121215)

摘　　要：对青海省纳日贡玛斑岩钼铜矿床开展了锆石LA-ICP-MS U-Pb同位素定年研究,结果表明,纳日贡玛矿区2个黑云母花岗斑岩样品的锆石206Pb/238U同位素加权平均年龄分别为(43.4±0.4)Ma和(42.9±0.3)Ma,锆石形态、结晶振荡环带结构及元素含量均显示出岩浆成因特点;因此,锆石U-Pb年龄可代表斑岩的岩浆结晶年龄,纳日贡玛含矿斑岩岩浆的侵位年代可精确地限定于新生代喜马拉雅期,相当于中始新世。1件辉钼矿样品Re-Os同位素模式年龄为(40.8±0.4)Ma,结合前人的辉钼矿测试结果,认为在纳日贡玛岩浆活动约2.6 Ma后,岩浆热液成矿流体开始产生成矿作用。三江走滑断裂构造系统控制斑岩矿床的分布,青海三江北段斑岩钼铜矿具有很大的找矿潜力。Narigongma deposit,located in the northern section of the Sanjiang polymetallic ore belt,southern Qinghai Province, is a large reserve porphyry molybdenite-copper deposit.This study provides highly precise dating of the mineralization in Narigongma deposit.According to the results of LA-ICP-MS zircon U-Pb isotopic data,the 206Pb/238U weighted mean age of 33 analytical data from ZK004 is（43.4±0.4） Ma,with MSWD being 1.9,and the 206Pb/238U weighted mean age of 24 analytical data from ZK805 is（42.9±0.3） Ma,with MSWD being 0.6.These zircons have characteristics of magmatic origin,thus the zircon U-Pb isotopic dating can represent the ore-bearing rocks forming age.One piece of molybdenite sample from Narigongma deposit determined by ICP-MS shows that the Re-Os model age is（40.8±0.4） Ma.It can indicate that the mineralization was developed 2.6 Ma later than the intrusion of the porphyries.Strike-slip fault systems control the distribution of Sanjiang porphyry deposits,and the northern section of Sanjiang porphyries belt have great prospecting potential.

关 键 词：LA-ICP-MSU-Pb定年 黑云母花岗斑岩 斑岩矿床 纳日贡玛 青海省南部 

分 类 号：P618.41[天文地球—矿床学] P588.13[天文地球—地质学]